Peir Nts Section 24 Dcs

8/3/2019 Peir Nts Section 24 Dcs

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Section 24: Deptford Church Street

Preliminary environmental information report Page 290 Non technical summary

24 Deptford Church Street

24.1 Introduction

24.1.1 This section of the non-technical summary presents the preliminary

environmental assessment for the Thames Tunnel project at DeptfordChurch Street (Figure 24.1).

24.1.2 At this site it is proposed that the Deptford Storm Relief Sewer would belinked to the proposed Thames Tunnel through a shaft and longconnection tunnel from Greenwich Pumping Station. Currently, theexisting combined sewer overflow discharges approximately 36 timeseach year. The total volume of this discharge is 1,471,500m3 each year.The combined sewer overflow discharges into the River Thames atBorthwick Wharf, near the mouth of the Deptford Creek

24.1.3 In the following section a description of the existing site is given. This is

followed by a description of the development proposed at this site.24.1.4 The environmental topics which have been assessed for this site are listed

in the Assessment section (0). Preliminary assessment findings are thenpresented topic by topic.

24.2 Site context

24.2.1 The site is shown as site number 20 on Figure 28.1.

24.2.2 The site is located within the London Borough of Lewisham (Figure 24.1).It is also close to the London Borough of Greenwich.

Figure 24.1 Deptford Church Street site location


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24.2.3 The triangle of land which forms the site is located on an area of openspace adjacent to St Josephs Roman Catholic Primary School and southof St Pauls Church. Approximately just over half a hectare is required forboth the temporary construction works as well as the permanent works.This is indicated by the red line shown on Figure 24.2. The site is located

entirely inland and so requires no works within the foreshore at thecombined sewer overflow outfall.

24.2.4 Access to the site is from Coffey Street and Crossfield Street.

Figure 24.2 Aerial photograph of Deptford Church Street*

*Note: The red line boundary is approximate in this image

24.3 Proposed development

24.3.1 The proposal is to intercept the existing combined sewer overflow. Withthe Thames Tunnel in place, instead of untreated sewage discharging atcurrent volumes directly into the River Thames, flows would be divertedinto the Tunnel. For a typical year, this would reduce flows from thecombined sewer overflow at this site to an average of four spills a year attotal volume of 161,300m3 a year.

24.3.2 In order for this interception to be achieved, construction works at this sitewould take approximately four and a half years. Interception of theexisting combined sewer overflow would be undertaken in DeptfordChurch Street.


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24.3.3 A shaft with an internal diameter of approximately 17m and approximately46m deep would be constructed. Once constructed, the base of this shaftwould join up with the long connection tunnel from Greenwich PumpingStation. This long connection tunnel would run through the base of theDeptford Church Street shaft. Flows from the existing Deptford Storm

Relief Sewer would be diverted into the Greenwich connection tunnelthrough an interception chamber into the main tunnel.

24.3.4 In order to manage and mitigate effects on the environment duringconstruction, a Code of Construction Practice has been drafted. This setsout measures to be adhered to during the construction works.

24.3.5 Most of the construction would take place from 8am to 6pm, Monday toFriday. Limited works may be required beyond these hours. In order tosafeguard the environment during construction, a Code of ConstructionPractice has been drafted. This sets out measures to be adhered toduring the construction works.

24.3.6 Figure 24.3 shows an indicative plan of the construction works.

Figure 24.3 Indicative plan of construction works for Deptford Church Street


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24.3.7 Once the works at this site have been built, a number of permanentfeatures would be visible (Figure 24.4). There would be a kiosk housingequipment to control equipment located in the below ground chambers.This would be two and a half metres high.

24.3.8 There would also be three ventilation columns; two four metres high andthe other six metres high. The four metre ventilation column would berequired to allow air to be released when flows in the tunnel rise into theshaft. Air would be treated through underground filters and releasedthrough the ventilation column. The six metre column would be used torelease air from the interception chamber. There would be no operationallighting required.

24.3.9 Once the project is built and operational, there would be an area ofhardstanding provided to enable access into the shaft and the tunnel forinspection and maintenance purposes. Access for maintenance purposeswould be required every three to six months. Once every ten years more

substantial maintenance work would be required.

Figure 24.4 Deptford Church Street indicative plan of built development


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24.4 Assessment

24.4.1 Based on the existing site and the works proposed, the followingenvironmental topics have been included in the scope of this preliminaryenvironmental assessment:

a. Air quality and odour

b. Ecology aquatic and terrestrial

c. Historic environment

d. Land quality

e. Noise and vibration

f. Socio-economics

g. Townscape and visual

h. Transporti. Water resources (ground and surface)

j. Flood risk

24.4.2 In the following sections, information about the preliminary assessment ofeach of these topics is presented.

24.4.3 As part of the assessment process, consideration has been given toknown major developments that may change future environmentalconditions. There are no known developments in the vicinity of this site.Future environmental conditions are therefore not anticipated to change

significantly from those which exist today as a result of otherdevelopments.

24.4.4 Further information on the topic specific methodology for conducting theassessment is given in section 4 of this non-technical summary.

24.5 Air quality and odour

24.5.1 The Deptford Church Street site is located within one of the LondonBorough of Lewisham Air Quality Management Areas. Local monitoringdata indicates that there are currently exceedences of the air qualitystandards in the vicinity of the site. The nearest people who might be

sensitive to the development are occupiers of nearby residential dwellingsto the east of the site (between Deptford Church Street and Bronze Street)and nearby office and commercial properties to the south and west of thesite. Additionally there are the pupils and staff at St Josephs CatholicPrimary School and users of the nearby playground, leisure centre, libraryand St Pauls Church.

24.5.2 Based on this preliminary assessment, it is considered that the overalleffect on local air quality from construction road traffic and constructionplant is likely to be minor adverse at the residential properties, school andchurch, and negligible at the commercial/office premises, playground andleisure centre. In terms of construction dust, this is likely to have a minor

adverse effect at the school, and a negligible effect elsewhere, takingaccount of the dust control measures in the Code of Construction Practice.


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24.5.3 Preliminary assessment findings indicate that the effects of odoursreleased from the ventilation structure is likely to be negligible.

24.5.4 Based on this assessment, it is considered that mitigation measures arenot required.

24.6 Ecology aquatic24.6.1 The sewage outfall that would be intercepted currently discharges into the

River Thames and Tidal Tributaries Site of Metropolitan Importance. Theriver habitat at the discharge point west of Borthwick Wharf is an area ofgravel foreshore, underlain by cobbles and pebbles with some bouldersand sand (Figure 24.5). Data indicates a reasonably high diversity of fishspecies, but invertebrate diversity is limited.

24.6.2 There would be no in river works associated with this site. No furtherconsideration of the impacts associated with construction has thereforebeen undertaken for aquatic ecology.

24.6.3 During operation, the reduction in fish mortality that would result fromimproved oxygenation of the water in the vicinity of the site is considered amoderate beneficial effect. There is also considered to be a moderatebeneficial effect through increased distribution of rare and/or pollutionsensitive fish species in the longer term of operation. Increasedinvertebrate diversity, abundance and presence of rare and pollutionsensitive species is considered to have minor beneficial effects in thelonger term of operation. Effects on mammals would be negligible.

24.6.4 No mitigation is required at this site because only beneficial effects areanticipated.

Figure 24.5 Deptford Church Street aquatic ecology survey site onthe River Thames near the combined sewer overflow outfall.


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24.7 Ecology terrestrial

24.7.1 The site lies within the St Pauls Churchyard and Crossfield Street OpenSpace Site of Importance for Nature Conservation. Amenity grassland,scattered trees and scrub are present on site. There is limited potential forbats to forage on site. The vegetation on site is likely to support commonbreeding bird species.

24.7.2 Based on preliminary assessment findings, site clearance would result inthe loss of a small area of habitat and would have a minor adverse effecton the habitats bats and breeding birds. Disturbance from constructionactivities on bats is considered to be a minor adverse effect. All othereffects on breeding birds and invertebrates and Site of Importance forNature Conservation are considered to be negligible.

24.7.3 It is anticipated that operational activity would be limited to occasionalmaintenance work, which is considered unlikely to have significant effects

on terrestrial ecology.24.7.4 In addition to measures included within the Code of Construction Practice,

further mitigation, such as habitat creation will be developed as necessaryand reported in the Environmental Statement.

24.8 Historic environment

24.8.1 The site consists of a plot of open space which is currently unoccupiedapart from an earlymid 19th century boundary wall (of low heritage assetsignificance), which runs through the eastern part of the site. The sitecontains no nationally designated heritage assets. The Grade I listedChurch of St. Paul (of very high heritage asset significance) lies to thenorth of the site. The churchyard walls are Grade II listed (of high heritageasset significance). There is no evidence to suggest that the burial groundever extended into the site. A Grade II Railway Viaduct is locatedapproximately 15m to the south. The site is located within the locallydesignated St. Pauls Conservation Area (of high heritage assetsignificance).

24.8.2 The site lies within the Upper Deptford Archaeological Priority Area andthe main potential in terms of buried heritage is for post-medieval 18th,19th and early 20th century house footings, of low heritage assetsignificance. The site has generally low potential for prehistoric, Roman

and medieval remains, as it lay outside the main areas of settlement inthese periods.

24.8.3 The 19th century brick wall within the site would be removed duringconstruction, resulting in a minor adverse effect. Construction works wouldentail deep excavations which would entirely remove the assets within thefootprint of each area of construction. If any such assets were found to bepresent then this would comprise a high magnitude of impact and wouldlead to a minor adverse effect on post-medieval remains.

24.8.4 To mitigate the effect on the wall, the structure would be recorded in linewith accepted standards to form preservation by record. The desk-based

study of the site suggests that no buried heritage assets of very highsignificance are anticipated that might merit a mitigation strategy of


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permanent preservation in situ. Any adverse effects could be successfullymitigated by a suitable programme of archaeological investigation beforeand/or during construction, drawing on a range of techniques. This wouldinclude subsequent dissemination of the results and so achievepreservation by record. This mitigation would reduce the residual effect to

negligible.24.8.5 Effects on the historic environment arising from the operation of the

Thames Tunnel infrastructure at Deptford Church Street, on assetsincluding the St. Pauls Conservation Area and the historic setting of theChurch of St. Pauls and nearby listed structures, will be assessed andpresented in the Environmental Statement. Any mitigation requirementswill also be presented.

24.9 Land quality

24.9.1 A search of historical and environmental data indicated that there were no

contaminative on site uses. The site was previously occupied by housingwhich was cleared during the 1970s. Historically the surrounding areahas been developed for a number of industrial/commercial properties,notably towards the east and south of the site. There is also a boroughdepot and railway line located less than 15m south of the site. Desk basedstudies have identified a low/medium risk from unexploded ordnance.

24.9.2 Based on preliminary assessment findings, there may be a slight adverseeffect on construction workers due to the potential for exposure tocontaminated soils or other materials if they are present, although anyexposure risk would be short-term. There would be a negligible effect onthe built environment as it is considered unlikely that contaminantscontained in subsurface materials would affect buried structures. Thepreliminary assessment therefore identified no need for mitigation duringthe construction phase. The Environmental Statement will considerinformation from ground investigations and the potential for foreshoresediment contamination. During operation there would be negligible effecton future users and the built environment. The assessment identified noneed for mitigation during the operational phase.

24.10 Noise and vibration

24.10.1 The site is characterised by road traffic and rail noise. The nearest

locations to the site which are sensitive to noise and vibration areresidential dwellings at Congers House and Farrer House, St JosephsPrimary School to the south and St Pauls Church to the north.

24.10.2 Based on this preliminary assessment significant noise effects arising fromconstruction activities are predicted at residential properties on DeptfordHigh Street, Deptford Church Street, at Congers House and at St JosephsPrimary School. However, no significant vibration effects are predicted atany of the areas considered in the construction assessment. No significanteffects as a result of the operation of the site are predicted.

24.10.3 During construction activities, the contractor would be required to follow

best practice (as described in the Code of Construction Practice) at all


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times to reduce the noise and vibration effects upon the local communityfor example through suitable siting of equipment on site.

24.10.4 It is anticipated that mitigation would be required to address significantnoise effects. This could include the use of localised screens andenclosures to reduce noise from particularly noisy, static operations.

24.10.5 The next stage of the assessment will profile the variation in constructionnoise levels across the programme of work with the aim of refiningmitigation design and seeking to reduce the significant effects ofconstruction noise and vibration. Further details of mitigation measureswill be provided in the Environmental Statement including the significanceof residual effects once mitigation has been taken into account.

24.11 Socio-economics

24.11.1 The site comprises the entire Crossfield Street open space. Residentialdwellings, commercial properties, other open spaces and community

facilities, including St Pauls Church (Figure 24.6) and St Josephs PrimarySchool surround the site. The Crossfield Street open space is lightly usedfor walking and passive recreation. The adjacent open spaces aremoderately used.

24.11.2 During construction, there are considered to be moderate adverse effectson nearby residents, pupils at St Josephs Primary School and users of StPauls Church and Sue Godfrey Nature Park. The loss of CrossfieldStreet open space and amenity impacts on its users are considered toresult in negligible effects. There are not anticipated to be any operationalsocio-economic effects resulting from the use of the site.

24.11.3 In completing the assessment, there is scope for further constructionphase mitigation measures to be incorporated in the design with the aim ofseeking to reduce significant adverse amenity effects which have beenidentified in this preliminary assessment.

Figure 24.6 The churchyard of St Pauls Churchto the north of the site


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24.12 Townscape and visual

24.12.1 The site is located within the St. Pauls Conservation Area and comprisesa triangle of open space adjacent to the Grade I listed Church of St. Paul,surrounded by roads. The open space is characterised by amenitygrassland and scattered mature trees in a fair condition. The surroundingtownscape is dominated by a mix of industrial, residential and small scalecommercial premises.

24.12.2 Based on preliminary assessment findings during the construction phaseand due to the clearance of trees, presence of cranes and the intensity ofconstruction activity there would be a major adverse townscape effect ontownscape character areas at the site and St. Pauls Conservation Area.There would be a moderate adverse effect on Creek Road Residential andLaban Centre and Bronze Street Open Space, and a minor adverse effecton Creekside Residential and Deptford Residential due to a slight changein their setting. Once operational, preliminary assessment findings

indicate there would be minor to moderate beneficial townscape effects onthe site and St. Pauls Conservation Area due to the introduction of highquality public realm and negligible to minor beneficial effects on CreekRoad Residential, Creekside Residential, and Laban Centre and BronzeStreet Open Space. The level of significance is dependent on the finallandscape and architectural design and will be refined for theEnvironmental Statement.

24.12.3 In terms of visual amenity, during the construction phase, preliminaryassessment findings indicate there are likely to be major adverse effectson viewpoints including views from Deptford Church Street, Deptford High

Street and St. Pauls Church due to the visibility of hoardings, cranes andconstruction activity. There would be moderate adverse effects onviewpoints including from Creek Road, Bronze Street and Deptford ChurchStreet. There would be minor adverse visual effects on the view fromFerranti Park due to the background visibility of cranes. Once operational,preliminary assessment findings indicate that there would be minor tomoderate beneficial effects on viewpoints including from the junction atDeptford Church Street, Deptford High Street and St. Pauls Church due toviews of new public realm. There would be negligible to minor beneficialeffects on at the views from Bronze Street and Deptford Church Street dueto the partial visibility of new public realm. The level of significance is

dependent on the final design and will be refined for the EnvironmentalStatement.

24.12.4 Mitigation measures to be employed during the construction phase arebeing incorporated into the proposals, for example, through use of cappedand directional lighting when required. In terms of operation, a process ofiterative design and assessment has been employed to reduce adverseeffects and maximise beneficial effects. It is likely that there would be nosignificant adverse effects during operation and therefore no furthermitigation is proposed.


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24.13 Transport

24.13.1 The Deptford Church Street site has moderate public transportaccessibility and is within close proximity to Deptford National Rail stationand Deptford Bridge DLR station. Vehicle access is proposed fromCrossfield Street, with egress onto Coffey Street (Figure 24.7).

24.13.2 During construction, the number of heavy goods vehicle movements wouldbe moderate. Due to the location and nature of the construction site it isconsidered likely to result in a moderate adverse effect on road networkoperation and delay due to the necessary diversion routes, highway layoutchanges and delays to journey time. Effects on pedestrian facilities andcyclist amenity and safety are expected to be moderate adverse as aresult of the loss of footways, modifications to traffic lanes and localdiversions. A moderate adverse effect is also expected on the bus networkwithin the area as a consequence of the effects on the highway network. Anegligible effect is expected on rail and river services. During the

operational phase there would be very occasional vehicle trips to and fromthe site for maintenance activities but these would have a negligible effecton the surrounding transport networks.

24.13.3 The project is being designed to limit the effects on the transport networksas far as possible. At this location, mitigation measures during theconstruction phase are likely to be required and would take the form ofsafe crossing points for pedestrians and cyclists on the diversion routes,junction signal optimisation and measures to ensure the frequency of busservices. Mitigation is not required for the operational phase.

Figure 24.7 Coffey Street junction with Deptford Church Street


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24.14 Water resources - ground water

24.14.1 The shaft would pass through the upper aquifer and into the lower aquifer.Associated interception infrastructure would penetrate the upper aquifer.Both the upper and lower aquifers are sensitive environmental receptors.The lower aquifer is of high value and the nearby Thames Water Utilitiespublic water abstractions from it of very high value, while the upper aquiferis considered to be of medium value.

24.14.2 Construction effects on the upper aquifer would be the physicalobstruction of groundwater, which is anticipated to be negligible.Construction effects on the lower aquifer include dewatering which couldaffect groundwater resources and induce groundwater movement. Theeffect of dewatering in the lower aquifer is considered to be minor adverseon water resources but has the potential to have a major adverse effect onquality and requires further assessment.

24.14.3 At the operational phase, the main potential effects are the obstruction togroundwater flow and the risk from seepage into and out of the shaft.These effects are considered to be negligible for the upper aquifer andminor adverse for the lower aquifer at this stage.

24.14.4 Monitoring of groundwater levels and water quality will continue duringconstruction and operation.

24.15 Water resources surface water

24.15.1 The site is located a kilometre south of the River Thames and 300 metreswest of Deptford Creek. The section of the River Thames closest to thesite lies within a zone of the river defined by the Environment Agency asThames Middle waterbody, which is current classified under the WaterFramework Directive as being at moderate potential status, with a statusobjective of good potential by 2027. Deptford Creek is not assessed underthe Water Framework Directive however, as it forms part of the ThamesMiddle, which has a target status of Good by 2027, the Deptford Creekshould also be assumed to have a target status of Good. There are a nonationally or locally designated water-dependent conservation sites within2 kilometres of the site.

24.15.2 There is the potential for effects on surface water resources from theproposed construction works through surface water runoff and exposure of

the drainage system to contaminants. After taking into account themeasures incorporated into the design and Code of Construction Practice,such effects are expected to be not significant. No mitigation wouldtherefore be required.

24.15.3 Once operational, the scheme would reduce the number of dischargesfrom the Deptford Storm Relief combined sewer overflow to a predictedlevel of four spills per year.

24.15.4 This reduction would have a beneficial effect on water quality. The numberof risk days for river users being exposed to pathogens would be reducedby up to 128 days per year. In addition, the tonnage of sewage derived

litter can be expected to be reduced from approximately 370 tonnes to 30tonnes per year.


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24.16 Flood risk

24.16.1 The main source of flood risk to the site is the tidal River Thames. Thesite lies within the low probability and medium probability flood zones,although it is protected by flood defences which run along the river banks.

24.16.2 The site may also be at risk of localised surface water flooding due torunoff generated by land surrounding the site. Further studies are beingcompleted to assess the potential impacts.

24.16.3 The site is currently has no formal surface water drainage system. Thepotential increase in surface water runoff due to the proposed addition ofhard standing areas on site would be mitigated in accordance with currentplanning policy requirements.

24.17 Further information

24.17.1 Further information regarding preliminary assessment findings for Deptford

Church Street can be found in Volume 25 of the PreliminaryEnvironmental Information Report.

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